This invention relates to fluid check valves, and more particularly to an improved check valve structure wherein the valve assembly is a replaceable unit which can be positioned within a suitable housing, such as a union, which, in turn, can be connected to a fluid conduit.
In the past, check valves have generally been of an integral, unitary structure adapted to be directly connected to a fluid system. Generally, a valve seat was formed in a housing-like member, and a movable valve element was positioned within the housing for movement toward and away from the valve seat. One type of valve member frequently used in such valves is a ball, to provide a ball-type check valve wherein in the ball cooperates with a conical valve seat to provide a line-type seal so that fluid is permitted to flow in one direction but not in the other. Another type of known check valve structure involves a generally conical valve member which cooperatively engages with a generally conical valve seat, the valve member being spring biased against the valve seat, the spring force being such that flow through the valve is permitted only upon the pressure of the fluid attaining a predetermined level. Valves of the latter type are most often utilized in applications wherein a pressure relief valve is required in order to permit flow to take place from a pressurized system to relieve the pressure therein when it reaches a predetermined level. An example of a spring-operated, conical valve face pressure relief valve is shown in U.S. Pat. No. 3,054,422, which issued Sept. 18, 1962, to the inventor of the present invention.
Because the prior art valve structures incorporated the valve seat as a substantially integral part of the housing, or a part that, although removable, was cumbersome to remove, if the valve seat were damaged by corrosion, distortion, wear, or the like, the valve would require replacement with an entirely new valve, which oftentimes involved considerable time and expense. Consequently, it is desirable to provide a check valve structure wherein a replaceable valve assembly is utilized and thereby permit replacement merely of the valve and valve seat without the necessity for replacing the valve housing.